Understanding Redux Toolkit 2.0: Improvements and New Features

Anton Ioffe - January 6th 2024 - 10 minutes read

In the ever-evolving landscape of modern web development, the release of Redux Toolkit 2.0 marks a significant milestone—not only refining the developer experience but setting a new standard for robust state management. As we dissect this latest iteration, from its architectural overhaul to performance enhancements, you'll uncover the sophisticated new features it wields and the nuanced breaking changes it brings. Journey with us as we delve into this toolkit's enriched API surface, unearthing the profound implications for your applications, and chart a course for future-proof development practices. Whether you're seeking to amplify performance or streamline your Redux logic, prepare to have the potential of Redux Toolkit 2.0 unfurled before you in a narrative that promises to fortify your projects against the tides of change.

Redux Toolkit 2.0 - Architectural Revamp and Enhanced API Surface

Redux Toolkit 2.0 represents a significant evolutionary step in the Redux ecosystem, aiming at refining and streamlining the toolkit's architecture. A major facet of this revamp is the concerted effort to eliminate legacy patterns and deprecated options that have been known to clutter Redux applications in the past. With the focus on tightening up edge cases, the architectural rework has paved the way for a more consistent and predictable state management experience, as these revisions directly influence how developers structure and maintain their Redux logic.

One of the key aspects of this architectural overhaul is the introduction of a more modular and reusable API surface. Redux Toolkit's API now embraces modern JavaScript practices, providing developers with a concise and powerful set of tools that encourage better coding patterns. This modularity not only enhances readability and maintenance of Redux code but also significantly reduces the boilerplate often associated with Redux, allowing for more efficient state management and logic reuse across different parts of an application.

Consider the transition from the traditional Redux practice of combining numerous reducers to using the createSlice function:

// Before: A verbose approach with combineReducers
import { combineReducers } from 'redux';
import usersReducer from './usersReducer';
import postsReducer from './postsReducer';

const rootReducer = combineReducers({
  users: usersReducer,
  posts: postsReducer

// After: A modular approach with createSlice (RTK 2.0)
import { createSlice } from '@reduxjs/toolkit';

const usersSlice = createSlice({
  name: 'users',
  initialState: {},
  reducers: {/* ... */}

const postsSlice = createSlice({
  name: 'posts',
  initialState: {},
  reducers: {/* ... */}

In this example, createSlice automatically generates action creators and action types, promoting both modularity and reusability.

Additionally, Redux Toolkit 2.0 fortifies its commitment to developer ergonomics by refining the core API surface. The toolkit’s creators took a scrutinizing look at the various utilities and functions provided, optimizing them to ensure smoother integration and extension. This attention to detail ensures that the tools available are not just more potent but are also better harmonized with each other, offering a cohesive experience.

The improvements in structural modularity extend further into the realm of configurability and customization. Redux Toolkit 2.0 offers a more pluggable architecture, wherein developers can easily swap in and out middleware or enhancers as needed. This level of flexibility means that the toolkit can be adapted to fit a wide range of use cases, from simple applications to complex, large-scale enterprise systems.

// Configuring a store with middleware swaps becomes straightforward:
import { configureStore } from '@reduxjs/toolkit';
import logger from 'redux-logger';

const store = configureStore({
  reducer: {
    users: usersSlice.reducer,
    posts: postsSlice.reducer
  middleware: (getDefaultMiddleware) => getDefaultMiddleware().concat(logger),

In the above store configuration, the configureStore function from RTK 2.0 allows the integration of custom middleware like redux-logger, illustrating enhanced configurability.

Redux Toolkit 2.0’s evolution emphasizes a balance between offering a versatile and powerful library while also steering towards a simpler and more accessible future for state management within the JavaScript landscape. By dispelling the intricacies that once made Redux daunting for some, Redux Toolkit 2.0 provides a fresh perspective on the best practices for establishing a reliable state management pattern, substantially benefiting the modularity, reusability, and overall architectural integrity of contemporary Redux applications.

Performance Tuning and Optimizations in Redux Toolkit 2.0

In Redux Toolkit 2.0, performance enhancements are evident in the reworking of the createEntityAdapter API. This utility function simplifies the operation of managing normalized state, making commonly-required cases such as updating a single entity or handling a list of entities more efficient. Previous versions imposed overheads in searching and updating items within the state; however, the latest iteration offers methods like updateOne or upsertMany that provide more direct and thus quicker ways to perform updates. For instance:

const usersAdapter = createEntityAdapter();
const initialState = usersAdapter.getInitialState();

const userSlice = createSlice({
  name: 'users',
  reducers: {
    userAdded: usersAdapter.addOne,
    usersReceived(state, action) {
      usersAdapter.setAll(state, action.payload);
    userUpdated: usersAdapter.updateOne

// ...dispatch userAdded, userUpdated actions as needed

Memory usage is also a key consideration. By fine-tuning the use of memoized selectors with Reselect 5.0, Redux Toolkit reduces unnecessary recalculations and re-renders. Memoizing selectors help ensure that state slices are only recomputed when relevant state changes, rather than on every dispatch. Using factory selectors allows isolation of memoization per-component basis, which is a strategy for avoiding selector recomputations across different instances of the same component type. Here is how it can be leveraged:

import { createSelector } from '@reduxjs/toolkit';

const selectUserId = (state, userId) => userId;
const selectUserById = createSelector(
  [state => state.users, selectUserId],
  (users, userId) => users.entities[userId]

// Usage inside a component
const user = useSelector(state => selectUserById(state, props.userId));

Adhering to best practices for leveraging these performance optimizations is crucial. A good rule of thumb is to keep state normalization a priority, avoid deeply nested state structures, and make use of entity adapters for optimal memoization. When writing selectors, aim for composability and specificity, which not only makes them more maintainable but also ensures that they are efficiently tracking only the necessary portions of state.

Redux Toolkit 2.0 enhances performance further through intelligent use of middleware for side effects. Selective use of middleware eliminates unnecessary processing and focuses on efficient asynchronous patterns. For instance, an effective approach is to use listener middleware actions that respond to state updates without the additional overhead of more complex logic found in other middleware patterns:

import { createListenerMiddleware } from '@reduxjs/toolkit';

// Example of registering a middleware listener
const listenerMiddleware = createListenerMiddleware();
  actionCreator: actions.userUpdated,
  effect: async (action, listenerApi) => {
    // Perform side effect here in response to userUpdated action

Avoiding common pitfalls involves keeping an eye on selector complexity and middleware overhead. Excessive use of selectors that perform heavy computations can lead to lags, just as convoluted logic in middleware can increase processing time. It's wise to review the necessity of each piece of middleware in your configuration and ensure each selector is efficiently written and properly memoized. While Redux itself is inherently performance-focused, overextension beyond its intended use case without careful optimization can negate the benefits it offers.

New Features and APIs: Expanding the Redux Toolkit Paradigm

Redux Toolkit's latest release introduces a suite of features and API enhancements designed to revolutionize how developers implement Redux logic in their applications. One of the standout additions is the combineSlices API, which revolutionizes code-splitting by enabling dynamic injection of slice reducers. This addresses a common pain point in large-scale applications where managing the loading state of numerous reducers was cumbersome. Developers can now modularly load and unload reducers as needed, keeping the application bundle size in check while enhancing scalability.

Another significant update is the revamping of theming structures within Redux Toolkit applications. Previously, customizing and ensuring consistency across the themes could be a manual and error-prone process. The new theming APIs provide a systematic approach, allowing for greater consistency in UI theming and a stronger emphasis on web accessibility right out of the box. This reduces the redundancy in theme-related code and empowers developers to maintain a cohesive look and feel with less effort.

The transition to named exports in Redux Thunk simplifies the middleware usage within the toolkit. Instead of a default export, developers now have clear and explicit access to thunk and its extension withExtraArgument. While this change improves the clarity and readability of the imports used, it also empowers developers to quickly discern the capabilities and extensions applied to their Redux middleware, enhancing code maintenance and onboarding for new team members.

Redux Toolkit also continues to simplify plugin development. Aligning with new React versions, it handles peer dependencies more elegantly, thereby preventing version mismatches and ensuring smoother updates. This is particularly beneficial for projects that are continuously evolving and require a more streamlined dependency management process to minimize conflicts and reduce setup complexity.

Finally, enhanced support for guardrails in state management not only automates routine setups but also nudges developers towards best practices. Developers will appreciate how this helps set up boilerplate code more effectively, leading to more robust defaults and a reduction in the risk of state mutation. By providing these thoughtful defaults and further promoting best coding practices, Redux Toolkit ensures that the state management codebase is both secure and maintainable, thereby increasing overall developer productivity.

Breaking Changes in Redux Toolkit 2.0: Migration and Mitigation Strategies

The createReducer and createSlice.extraReducers now mandate the usage of the builder pattern in lieu of the previously accepted object syntax. This change enhances the readability and flexibility of reducer definitions.

// Deprecated: Object syntax in createReducer
const counterReducer = createReducer(initialState, {
  [increment]: (state, action) => state + action.payload,
  [decrement]: (state, action) => state - action.payload

// Replacement: Builder pattern for more explicit control over case reducers
const counterReducer = createReducer(initialState, (builder) => {
    .addCase(increment, (state, action) => state + action.payload)
    .addCase(decrement, (state, action) => state - action.payload);

Middleware specification within configureStore has been altered to require a callback approach, thus removing the direct array or object assignment. This update serves to increase composability and type safety of middleware.

// Deprecated: Direct array or object for middleware
const store = configureStore({
  reducer: rootReducer,
  middleware: [thunkMiddleware, loggerMiddleware]

// Replacement: Callback providing access to default middlewares
const store = configureStore({
  reducer: rootReducer,
  middleware: (getDefaultMiddleware) =>
    getDefaultMiddleware().concat(thunkMiddleware, loggerMiddleware)

Transitioning from the createStore from Redux core to Redux Toolkit's configureStore is strongly encouraged to affirm consistency across store configurations.

// Deprecated: Using createStore from redux directly
import { createStore } from 'redux';
const store = createStore(rootReducer);

// Replacement: configureStore ensures conforming setup
import { configureStore } from '@reduxjs/toolkit';
const store = configureStore({ reducer: rootReducer });

The redux-thunk package shifts to named exports which offers a more explicit middleware structure.

// Deprecated: Default import of thunk from redux-thunk
import thunk from 'redux-thunk';

// Replacement: Named import ensures correct middleware reference
import { thunk } from 'redux-thunk';

// Apply withExtraArgument for custom argument passing
const thunkMiddleware = thunk.withExtraArgument(extraArgument);

To align with Redux Toolkit's latest standards, developers must migrate to the new builder API for reducers, use callback functions for middleware setup, and leverage named exports for thunks. Adopting these patterns is crucial for a coherent and maintainable codebase.

Future-Proofing with Redux Toolkit 2.0: Best Practices and Thoughtful Considerations

Adopting Redux Toolkit 2.0 urges a proactive approach to state management, necessitating developers to evaluate and adapt to ensure compliance with new patterns and practices. One of the core aspects of this transition is the conscientious use of the toolkit in a way that anticipates and prepares for both present requirements and future shifts. To sustainably harness the benefits of Redux Toolkit 2.0, developers should consider their use of state composition and slice management. Modularizing state effectively across slices not only facilitates easier maintenance and scaling but also positions your application to smoothly integrate with forthcoming advancements in state management paradigms. Are your slices designed with isolation and reusability in mind to cope with evolving business logic?

A thoughtful consideration is the emphasis on robust typing and enhanced type inference, especially for TypeScript users. Typings in Redux Toolkit 2.0 can significantly boost developer productivity and code quality, providing strong assurances about the shape and flow of state throughout the application. As you implement features, it’s advantageous to ask if the usage of types adds clarity and guards against possible mismanagement of state, thereby future-proofing your application against errors that arise from changes in state shape or associated logic.

Moreover, as new features and improvements continue to be introduced, it behooves developers to align with the best practices Redux Toolkit 2.0 advocates, such as leveraging the full capability of thunks and other async logic tools. The enhanced listener middleware, for example, enables more intuitive responses to state changes. In crafting your async routines, consider the trade-offs between competing patterns, such as thunks versus sagas, and the implications they may have in terms of code complexity and testability when aligning your application with future development in Redux Toolkit.

One often underestimated aspect is the diligent application of memoized selectors with the updated Reselect library. As applications scale, inefficient selector patterns can become performance bottlenecks, leading to unnecessary re-renders and sluggish user interfaces. Developers should regularly evaluate whether their selectors are optimized for the current state shape and are prepared for potential state structure changes in the foreseeable future. Could the selectors you're using now become a liability as demands on the application’s responsiveness grow?

Lastly, a forward-looking perspective on middleware selection and proper side effect management can’t be overstated. The choice and configuration of middleware have profound impacts on the application's capability to handle present and future complexities. A pivotal question to ponder is whether your current middleware setup provides the necessary capabilities for today's requirements while being adaptable enough to accommodate tomorrow's innovations. Does your middleware choice provide a sustainable foundation for the long-term adaptability of your application’s state management strategy?


The article "Understanding Redux Toolkit 2.0: Improvements and New Features" explores the advancements and enhancements in Redux Toolkit 2.0, focusing on the architectural revamp, improved performance, new features, breaking changes, and future-proofing. Key takeaways include the modular and reusable API surface, improved performance tuning with createEntityAdapter and memoized selectors, expanded features like combineSlices and theming structures, and the need to migrate and adopt best practices. The challenging task for readers is to evaluate their state management strategy, consider the use of slices and modularization, and ensure proper implementation of typing, memoized selectors, and middleware for future-proofing their Redux applications.

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